Fabric Mercerising Machines:
2. Pad Chainless Mercerizing Machine
There are three types of fabric mercerising machines:
1.
Pad
Chain Mercerizing Machine
2.
Pad
Chainless Mercerizing Machine
3.
Padless
Chainless Mercerizing Machines
1. Pad Chain Mercerizing Machine
A typical clip chain
mercerizing machine for woven cloth is shown in Fig. In this type of
mercerizing machine shrinkage is allowed in the primary stage of the process
and tension is applied in the later stage to bring the material to the original
dimensions. The cloth is impregnated with cold concentrated caustic soda
solution by passing through padding mangles.
 |
| Pad Chain Mercerizing Machine |
In between the padding
mangles the cloth is passed over timing drums to allow thorough action of
alkali on the cloth. The cloth is led to an open stenter frame for applying
tension both the filling and warp direction. After the cloth has traveled about
20 ft in a stretched condition alkali is rinsed from the fabric by overflowing
water from a series of cascades. The washing on the stenter can be carried out
in a counter current system. The residual alkali concentration should not be
more than 8% on the cloth. After leaving the stenter the cloth passes over
compensating rollers which regulate the tension. The cloth is squeezed and
washed. These washing units are the final portion of the mercerizing range and
may be a series of 7 to 8 washers followed by neutralizing washer using either
sodium bicarbonate or acetic acid.
The chain mercerizing
machine has one inherent disadvantage. As the force for keeping the material
under tension acts mainly on the outer edges and the line of force diminishes towards
the middle, a greater elongation takes place at the edges than in the middle of
the fabric shown in Fig.
 |
| Chain Mercerizing Machine |
2. Pad Chainless Mercerizing Machine
Diagram shows a
traditional chainless mercerizing machine with the roller arrangement. In this
system the fabric is pre stretched, tension is maintained till the mercerizing
process and after-washing are completed. The cloth enters the padding set-up
exactly in a similar manner to that of chain type. The cloth after padding with
mercerizing liquor is passed through specially curved and specifically
dimensioned expander rollers which make possible an even expanding effect over
the whole width. The expansion depends on the diameter of the roller, the
curvature of the roller as well as the angle of warp.
 |
| Pad Chainless Mercerizing Machine |
3. Padless Chainless Mercerizing Machines
In
padless chainless mercerization machine the fabric is just soaked in NaOH
solution and then after giving dwell time of 40-45 sec stretched on the
expander rollers as on chainless machines. Then the fabric is washed and
neutralized.
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